In a blender, combine the tomatoes, onion, garlic, water, and salt. Puree until smooth. Set aside. Preheat the oven to 350°F. Lightly oil a 13 × 9-inch baking dish.
Heat the olive oil in a large heavy saucepan over medium-low heat. Add the broken pasta and saute, stirring frequently to avoid burning, until deep golden brown. Add the chiles and cook, stirring, 2 minutes longer. Stir in the tomato puree and the stock or water and bring to a simmer. Pour into the baking dish.
Cover with aluminum foil and bake 10 to 15 minutes, until all the liquid has been absorbed and the noodles are tender. Uncover and sprinkle the cheese over the top. Turn the oven temperature up to 400°F and bake, uncovered, an additional 10 minutes, or until bubbling and golden. Arrange the avocado slices on top, sprinkle with the cilantro, drizzle with the crema if desired, and serve.
Variation: Saute 1 pound mushrooms, sliced, with 1 onion finely diced, and 1 small bunch epazote, leaves only, in olive oil and stir into the fideo mixture before baking.